1. Field of the Invention
The present invention relates generally to a multi-layer thin-film wiring board on which electronic components such as LSIs are mounted, and more particularly to a multilayer thin-film wiring board applicable to an MCM (multichip module) allowing high-density wiring.
2. Description of the Related Art
In recent years, a thin-film wiring board allowing high-density wiring, or a so-called MCM (multichip module) board, has been put to practical use. The MCM board usually employs polyimide as the material of a dielectric. A very thin dielectric layer can be formed by spin coating. Further, a signal pattern is formed by sputtering and etching using a high-sensitive resist. Accordingly, the pattern can be formed with a high density incomparable with that of a usual printed wiring board. For example, the requirement of wiring of all signal lines can be met by only two layers, thus allowing high-density wiring. In manufacturing a multilayer thin-film wiring board to be applied to such an MCM board, the common use of components such as a power supply layer and a ground layer in the multilayer thin-film wiring board is desired to reduce the costs in flexible manufacturing.
Conventionally known is a multilayer thin-film wiring board formed by laminating a plurality of wiring layers together with a dielectric layer. The wiring layers are, for example, a power supply layer, a ground layer, and a signal layer. The power supply layer and the ground layer are connected through vias to via pads formed on the surface of the wiring board, and electric power is supplied from either via pad through a footprint to a component such as an LSI. The signal layer is composed of two layers as two separated orthogonal components, i.e., X and Y components.
In applying the conventional multilayer thin-film wiring board mentioned above to flexible manufacturing, the pattern shapes of the power supply layer and the ground layer are specifically designed for various products, and the commonality of these wiring layers is limited.